Effect of hyperthermia induced by a high ambient temperature on the direct cortical response

Abstract

The direct cortical response in the supresylvian gyrus during hyperthermia and after restoration of temperature homeostasis was investigated in acute experiments on anesthetized cats kept in a hot chamber in which the air temperature was 45°C. As soon as the body temperature reached 40°C hyperthermia began to cause initial inhibition, followed by total disappearance, of the slow negative potential, and only when the temperature exceeded 43°C was gradual depression of the dendritic potential found. Restoration of normothermia after preceding hyperthermia was accompanied by a slight tendency for the parameters of the slow negative potential to return to normal. Analysis of changes in the dendritic potential to paired stimuli showed that a high temperature affects chiefly the presynaptic components of axodendritic cortical synapses. On the basis of the differential action of heat on the various components of the direct cortical response it is concluded that functionally different cortical cells differ in their sensitivity to hyperthermia.